1. Field of the Invention
The present invention relates to a robot system employed for various applications which use an industrial robot and, more particularly, to a technique for reproducing a situation in which an alarm is issued in the case where the robot or an object mounted or held thereon clashes with something.
2. Description of the Related Art
If trouble occurs at a robot which performs an operation designated by an instruction such as a command in a taught operation program or the like, it generally means that the external environment or the internal conditions which have been assumed for the operation of the robot have been changed. A robot system should be built such that such a situation can rarely occur. However, in the event that such a situation occurs, the system is unavoidably stopped quickly to secure safety.
On the other hand, in an application, for example, for taking each workpiece out of bulk workpieces, the robot is required to perform the operation according to the circumstances so that the robot changes its motion each time depending on irregular positions of the workpieces. In other words, the external environment is so unstable in such an application that it is not uncommon to issue an alarm relating to the contact or clash with comparative frequency. Therefore, if the system is stopped each time the alarm is issued, the working efficiency would be greatly deteriorated.
Techniques to avoid this inconvenience are disclosed, for example, in Japanese Patent No. 2662990 and Japanese Unexamined Patent Publication No. 2000-263481. The techniques described in these two patent documents concern a method of automatically restoring the system upon occurrence of a trouble, and these techniques make it possible to reduce the frequency at which the system is stopped and to improve the operating efficiency. However, there is raised a problem that a desire to know a situation in which the alarm is issued cannot be easily satisfied.
On the other hand, the techniques for knowing the temporally past phenomenon and the conditions at a spatially remote place are described, for example, in Japanese Unexamined Patent Publications No. 10-309683, No. 2001-179668 and No. 2001-277163.
The Japanese Unexamined Patent Publication No. 10-309683, which relates to a robot and a method of analyzing an error caused by the robot, discloses the technique to record-data relating to a control for a motor, such as the operating waveform or the like data of the motor, for the purpose of subsequent analysis.
Japanese Unexamined Patent Publication No. 2001-179668, which relates to a robot system for coping with accident, discloses a technique for monitoring a circumstance of an accident at an remote place using a monitoring device, such as a camera or the like, and a robot manipulator. Specifically, the point of this technique is to prepare a monitoring device operable at a remote place to grasp the circumstance of the remote place.
Further, Japanese Unexamined Patent Publication No. 2001-277163 relates to a robot controller and a robot control method. A feature of the technique described in this document is that a system behavior plan and the result of operation based on the plan are stored in a log. Specifically, in this technique, information on the operation is logged to permit subsequent analysis of an operational status of a mobile robot.
In the event of some failure in the robot system, it is desirable to take a preventive measure to avoid such a failure in the future. This requires analysis of the phenomenon. However, such an analysis is difficult in the case where the system has the ability to automatically restore itself without stopping the operation. The ability to automatically restore itself, therefore, is not always contributive to a reduction in the frequency of the trouble. In other words, the technique described in Japanese Patent No. 2662990 or Japanese Unexamined Patent Publication No. 2000-263481 is simply to automatically restore the system and provides no means for subsequent analysis of the cause of the trouble. Therefore, even though the system may be restored automatically, the system is finally required to be stopped in order to investigate the cause of the alarm, while no data useful to investigate the cause of the alarm can be obtained.
Also, in the techniques described in Japanese Unexamined Patent Publications No. 10-309683 and No. 2001-277163, only specific data are collected and it is difficult to reproduce the trouble that has actually occurred. Further, the technique described in Japanese Unexamined Patent Publication No. 2001-179668 has no ability other than to confirm the phenomenon such as an accident at a remote place, or the like, in real time.